Napier's Rods

Irene Santos                   Alexander Graham School
                               74 West 45th Street
                               Chicago IL 60609
                               (312)535-1315

Objectives:

Reinforce multiplication facts.
Examine Napier's Rods in relationship to multiplication.
Enhance students ability to understand place value.

Materials Needed:

Napier's grid sheet *
Tongue depressors or popsicle sticks (11 per student)
Scissors
White glue

Recommended Strategy:

Place simple multiplication problems on the board using one digit multiplier
and one digit multiplican.  Have the students come up to the board to work out 
the problems.  As a group check answers. 

Introduce Napier's Rods as a device related to multiplication.

Pass out the materials. 

Cut the grids into vertical strips.
Glue these to the sticks, thus making "rods".
Cover one side only on the sticks.

To see how the rods work, find 3 x 46 by placing, side by side, these rods:
INDX, 4, and 6. You should have 3, 1 over 2, 1 over 8.
Add these numbers diagonally making sure to add the numbers within their 
columns.  So, 3 x 46 = 1 3 8

These rods also will work for multiple-digit factors.  You probably will have to 
write down each partial product as you work.

Performance Assessment:

Evaluation will consist of correct products and checking to make sure rods are 
properly lined up so that diagonal adding keeps digits in proper place value 
column.

Reference:

  Math Activities With Simple Equipment, Dr. John L. Ginther.
Book can be found in the file cabinet in the math room.